This invention relates to a dental handpiece. More particularly, it relates to a cartridge type dental handpiece in which a cartridge for receiving and securing a dental burr is removably attached to a head housing provided at a distal end of the handpiece.
There have hitherto been employed a variety of so-called cartridge type dental handpieces in which a burr sleeve for secrring a dental burr and bearings for rotatably holding the burr sleeve are housed within a cartridge which is removably attached to a head housing provided at the distal end of the handpiece. The dental handpiece is provided with a spray unit for spraying a cooling fluid, such as water or air to a site of treatment for cooling the site during tooth cutting. In conventional cartridge type dental handpieces, such spraying units as shown in FIGS. 3 and 4 are employed. In an example shown in FIG. 3, air, water or a mixture thereof is sprayed to the site of treatment via an air supply port 52 and a water supply port 53 provided in the handpiece main body and communicating with an air-supply channel 50 and a water-supply channel 51, respectively. In an example shown in FIG. 4, the lower end face of the head housing 55 is planar and a front cap 57 having a recess or groove is mounted in intimate contact with the planar lower end surface of the head housing 55 for establishing an annular fluid passage 56 to which air and water are supplied via an air-supply port 52 and a water-supply port 53 opened on the lower end surface of the head housing 55 so as to be sprayed via fluid ejecting ports 58, 59 provided at predetermined positions within the fluid passage 56.
However, the conventional spray unit shown in FIG. 3, while having an advantage that the head is neat in appearance so that the site of treatment may be viewed more easily, is disadvantageous in that the opening positions of the air-supply port 52 and the water-supply port 53 are remote from a dental burr 60, while the fluid can be sprayed only in one direction proceeding from the handpiece main body to the site of treatment, so that the cooling effect is diminished, with the fluid being unable to reach the site of treatment particularly when cutting the lateral side of the tooth or cutting through the inside of the tooth.
While the conventional spray unit shown in FIG. 4 has an advantage that the fluid may be sprayed from many directions by providing plural fluid ejecting ports 58, 59 along the fluid passage 56, and spraying may be made from positions close to the site of treatment with improved cooling effects, the spray unit raises a problem that the field of view is interrupted during treatment by an enlarged lower head end, while the operation of attaching the front cap 57 to the lower end face of the head housing 55 in intimate contact therewith cannot be achieved without considerable difficulties.